This invention relates generally to coil winding machines for winding toroidal cores, and more particularly, to an improved core holder assembly adapted to provide continuous and accurate winding of precision wound toroidal cores.
Coil winding machines of the type useful for practicing the present invention utilize a revolving or circulating wirecarrying shuttle for winding a wire strand continuously about an exposed arcuate segment of the annular wall of a closed toroidal core, the core being supported in a manner to permit rotation of the core about a central axis thereof to selectively expose other arcuate segments for being wound to form the number of coils of wire comprising the windings of a toroidal core. The difficulties involved in existing machines and their ancillary support apparatus relate to providing suitable support members which do not interfere with the winding of the wire strand about the annular wall or with the passage of the shuttle through the central opening of the toroidal core; providing for the capability to rotate the core through a full circle without remounting the core with respect to the support apparatus due to mechanical interference between this apparatus and the shuttle; providing a uniform driving mechanism for rotating the core so that the accurate spacing of the axial loops of wire of each individual coil such as would be required for precision winding can be accomplished; and providing for securing these axial loops against misalignment or lateral movement along opposite rim portions of the toroidal core that could cause field distortion for the current-carrying coils.
One existing type of support structure for the toroidal core is a clamp which engages at least aligned portions of the opposite rims or ends of the core for leaving the remaining rim or end portions free; however, the core must be repositioned within the clamp for full circular utilization of these rim portions. Another winding technique is to rotate the core on fixed supports to continuously expose a free segment of the core to the circulating shuttle and its wire strand. This technique requires an interface with the core that will not vary in rotating speed with subsequent build-up of layers of coil such as is inherent in using revolving wheels that frictionally engage the annular wall.
In some core support or holder assemblies, the core is completely encased within a core holder form that is constructed of a material like plastic which will not appreciably interfere with the magnetic field characteristics of the core. Some core holder forms are provided with outwardly-extending radial ribs which can then be grasped by rotating drive mechanism to turn the core with respect to its support structure. Also, the core holder forms are provided with opposite rim portions covering the rim portions of the core for providing radial grooves therein in which to deposit the axial loops of wire thereby to prevent misalignment or lateral displacement. These radial grooves must be aligned properly between opposite rim portions, and the rotating mechanism must be correlated so that the circulating wire strand is deposited therein. It is desirable to provide a core holder form which allows the wire strand to be deposited directly across the rim portions of the core to form the axial loops while simultaneously preventing coil deformation caused by movement of the wire along these rim portions.